Saturday 11 January 2020

Asteroid 2008 LW16 passes the Earth.

Asteroid 2008 LW16 passed by the Earth at a distance of about 16 979 000 km (44.2 times the average distance between the Earth and the Moon, or 11.3% of the distance between the Earth and the Sun), slightly after 11.55 am GMT on Saturday 4 January 2020. There was no danger of the asteroid hitting us, though were it to do so it would have presented a considerable threat. 2008 LW16 has an estimated equivalent diameter of 210-650 m (i.e. it is estimated that a spherical object with the same volume would be 210-650 m in diameter), and an object of this size would be predicted to be capable of passing through the Earth's atmosphere relatively intact, impacting the ground directly with an explosion that would be 17 500-800 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater 3-9 km in diameter and devastation on a global scale, as well as climatic effects that would last decades or even centuries.

 The calculated orbit of 2008 LW16. Minor Planet Center.

2008 LW16 was discovered on 15 June 2008 by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2008 LW16 implies that it was the 406th asteroid (object W16 - in numbering asteroids the letters A-Y, excluding I, are assigned numbers from 1 to 24, so that W16 = (24 x 16) + 22 = 406) discovered in the first half of June 2008 (period 2008 W).

2008 LW16 has an 402 day orbital period and an eccentric orbit tilted at an angle of 29.7° to the plane of the Solar System, which takes it from 0.96 AU from the Sun (i.e. 96% of the the average distance at which the Earth orbits the Sun) to 1.18 AU from the Sun (i.e. 118% of the average distance at which the Earth orbits the Sun). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). This means that close encounters between the asteroid and Earth are extremely common, with the last having occurred in July last year (2019) and the next predicted in June this year (2020). As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2019 AV2 is also classified as a Potentially Hazardous Asteroid.

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